Demographic, perioperative, biochemical and illness‐severity predictors of thirst in critically ill patients: a systematic review and meta‐analysis

Thirst is a prevalent and distressing symptom among critically ill and surgical patients, yet its predictors remain poorly characterised. We aimed to quantify the associations between patient demographics, treatment modalities, biochemical markers and illness severity with self‐reported thirst in critical settings. We conducted a systematic review and meta‐analysis of studies published through April 2025 in PubMed, Embase, Web of Science, Cochrane Library and Ovid MEDLINE. Eligible observational studies in adult intensive care or perioperative cohorts reported associations between thirst and at least one of six factors: sex, anaesthetic technique, mechanical ventilation, blood urea nitrogen (BUN), serum osmolality or Acute Physiology and Chronic Health Evaluation (APACHE‐II) score. Data were pooled using DerSimonian–Laird random‐effects models to estimate odds ratios (ORs) for dichotomous predictors and weighted or standardised mean differences (WMDs/SMDs) for continuous variables. Heterogeneity was assessed by I 2 . Fifteen studies ( n = 11 657) met inclusion criteria. Sex (OR = 1.04 (95% confidence interval (CI): 0.95–1.14) I 2 = 0%) and mechanical ventilation (OR = 1.36 (95% CI: 0.91–2.05) I 2 = 63%) were not significantly associated with thirst. Anaesthetic technique (OR = 1.43 (95% CI: 0.97–1.89); P < 0.001; I 2 = 57%). APACHE‐II score (WMD = 0.24 points (95% CI: −0.55 to 1.04); I 2 = 26%) and BUN (SMD = 0.27 (95% CI: −0.11 to 0.65); I 2 = 84%) showed no significant effects. Serum osmolality exhibited the strongest relationship, with a mean elevation of 3.04 mOsm/kg in thirsty patients (95% CI: 0.15–5.93 ( P = 0.039); I 2 = 85%). Among the factors examined, elevated serum osmolality most reliably predicts patient‐reported thirst. Incorporating osmolality‐guided monitoring and tailored oral‐care protocols into critical‐care pathways may help pre‐empt and alleviate thirst, enhancing patient comfort in high‐acuity environments.